The research programs involve: (1) comparative studies on chemical, immunological, and biological nature of human chorionic gonadotropin (hCG), and of hCG-like substance in pituitary and urinary extracts, (2) production and characterization of specific antibodies against synthetic peptides based on the unique amino acid sequence of beta-subunit of hCG and the development of immunoassay methods for clinical and laboratory applications, and (3) examination of biological role of hCG-antibody complexes with relation to fertility regulation.